MQTT (Message Queuing Telemetry Transport, Message Queuing Telemetry Transport) is an instant messaging protocol developed by IBM, which may become an important part of the Internet of Things. The protocol supports all platforms and can connect almost all Internet-connected objects to the outside world, and is used as a communication protocol for sensors and actuators (such as connecting houses through Twitter).
It's actually very simple. TCP/IP protocol. Subscription and non-subscription;
Port with protocol design: 1883